The present invention relates to a thermal spray powder comprising granulated and sintered yttria particles and a method for forming a thermal spray coating in which such thermal spray powder is used.
In the field of producing semiconductor devices or liquid crystal devices, micro-fabrication of the device is conducted by dry-etching using plasma. During this plasma process, some portions of the semiconductor device production equipment or liquid crystal display device production apparatus may be liable to etching damage by the plasma. However, techniques are known (e.g. Japanese Laid-Open Patent Publication No. 2002-80954) for improving the plasma etching resistance of such portions by providing a thermal spray coating thereon. By improving plasma etching resistance in this manner, scattering of particles can be suppressed, and as a result, the device yield improves.
Thermal spray coatings which are used for this purpose can be formed by plasma-spraying a thermal spray powder comprising, for example, granulated and sintered yttria particles. Development of such thermal spray powders have been attempted to enhance the plasma etching resistance of thermal spray coatings against different types of plasma, such as high-power plasma and low-power plasma. However, none of granulated and sintered yttria powders have satisfied yet performance requirements.